Charging and/or printing unit for electrophotographic processes



Jan. 14, 1964 K. M. OLIPHANT 3,117,501 CHARGING AND/0R PRINTING UNIT FOR ELECTROPHOTOGRAPHIC PROCESSES 2 Sheets-Sheet 1 Filed Aug. 30, 1960 227% III II NVENTOR. KEWH MER DiTH OUPHANT J m 1 1964 K. M. OLIPHANT 3,117,501

CHARGING AND/OR PRINTING UNIT FOR ELECTROPHOTOGRAPHIC PROCESSES Filed Aug. 30, 1960 2 Sheets-Sheet 2 llIl-llllll' INVENTOR. KErrH MEFUDVTH OLIPHANT' United States Patent 3,117,501 CHARGTNG AND/R PRINTING UNIT FOR ELECTROPHOTOGRAPHIC PROCESSES Keith Meredith Oliphant, Westbourue Park, South Australia, Australia, assignor to Electrograph Research Limited, Adelaide, South Australia, Australia Filed Aug. 30,1960, Ser. No. 52,912 Claims priority, application Australia Sept. 3, 1959 Claims. (Cl. 95--1.7)

This invention relates to an improved charging and/ or printing unit for electrophotographic processes.

It is well known that when reproducing drawings, photographs, documents or the like by the electrophotographic method it is first necessary to charge the paper and to then produce the image thereon by bleeding away the charge at the required areas.

This is usually achieved by placing the paper into, or passing it through, a charging zone Where the photoconductor surface on the paper is subjected to a high voltage field such as a corona discharge, after which the paper is subjected to the light image which then bleeds away the charge where the light strikes the surface, in proportion to the amount of light, after which develop ment of the image so produced can take place by any of the known methods.

Various problems exist, however, in the charging of paper by the known methods, partly due to the. difiiculty of providing space for a large sheet of paper and the problem of moving it in a charging field which tends to cause the paper to hold on to the base due to static electricity and therefore makes it diflieult to move the paper past the charging point. As the charging point carries high voltage, certain problems also exist in connection with that, and it is therefore the object of this invention to provide an improved apparatus which, if desired, can effect both the charging and the printing in the one mechanism but in which the processes can'be carried out separately if necessary.

Briefly the invention comprises a member on which the paper to be charged and printed is mounted and over which member the charging and printing element moves at the required controlled speed, the element carrying charging means and the printing light so that a sheet may be charged and exposed through a negative or the like ready for development.

In order that the invention maybe more clearly understood, an embodiment thereof will now be described with reference to the accompanying drawings in which:

FIG. 1 is a sectional side elevation of the unit,

FIG. 2 is a front elevation thereof with part of the protective case removed,

FIG. 3 is an enlarged detail of the charging roller support and drive and the pressure roller supports, the view being taken from end but in part section,

FIG. 4 is an enlarged detail of the holding clip, and

FIG. 5 is a modified light and charging system where simultaneous charging and exposure takes place.

According to the construction illustrated in FIGS. 1 to 4 a vertically place main frame 1 has on it a clip 2 which is mounted on arms 3 at each side pivoted to the frame 1 and is opened by foot pressure on apedal 4 connected to the arms 3 by a link 5, a spring 6 urging the clip 2 into its closed position.

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A sheet 7 is pushed into position when the clip 2 is opened and will then be held suspended by the clip againsta backing plate 8 when the opening pressure is released from the pedal 4.

The front of the frame 1 forms a pair of tracks 9 which guide a transversely positioned carrier 10 which is moved on the tracks 9 by means of a pair of endless chains 11 so that it can traverse the whole of the area of the backing plate 8 on which the paper is suspended. The chains are supported on sprockets 12 and 13 carried on shafts 14 and 15 on the frame 1, the lower shaft 14 having the sprockets 12 secured thereto and driven through a gear box 16 from a motor 17. The motor 17 can be driven in either direction to cause the carrier 10 to be raised or lowered as required.

The carrier 10 supports on it a spiked charging roller 18 the shaft 19 of which is supported in insulating bearings 20 on the end plates of the carrier 10. The roller 18 is driven through a rubber wheel 21 which contacts both the roller 18 and the plate 8 to revolve the roller 18, as the carrier 10 is moved up and down, the roller 18 being carried on an arm 22 which is slidable on a pin 23 fixed to the end plate of the carrier 10 and is urged forward by a spring 24 to hold the Wheel 21 in contact with the roller 18 and the plate 8.

The bearings 20 are formed of an insulating medium so that the required high voltage can be applied between the roller 18 and the backing plate 8. A cover 26 extends over the charging roller 18 to prevent contact therewith during operation. The distance between the charging roller and the backing 8 can be varied by moving the insulated bearings 29 in slots 27 under control of threaded adjusting screws 28 which engage the bearings 29.

During charging the paper or sheet 7 is forced down on to the backing plate 8 by the electrostatic charge generated on the paper, and generally tends to adhere uniformly to the plate 8.

The foregoing mechanism serves to charge a xerographic sheet of paper or the like (such as the sheet 7) as the charging roller is moved over the backing 8.

Also positioned on the carrier 10 is a light source 30 located in a housing 31 having a slot 32 therein, the housing being encircled by a sleeve 33 with an opening therein so that by revolving the sleeve 33 on the housing 31, the effective width of the slot 32 can be varied, and thus the light value reaching the sheet 7 is regulated.

The housing 31 is fixedly supported from the carrier 16, but adjacent to the housing are a pair of rollers 35 and 36 which are carried on arms 37 pivoted on pressure bars 38 which are located by links 39 on the end plates of the carrier 10 and by levers 40 also pivoted to the end plates of the carrier 10, springs 41 causing the rollers 35 and 36 to be urged on to the backing plate 8.

The rollers 35 and 36 serve to overcome the ditficulty which exists where a large sheet must have a negative pressed on to it. The present invention utilises the pair of rollers 35 and 36 as said, which are resilient and which are spaced slightly apart as shown and are mounted so that they traverse the photo-conductor surface and allow the light source 30 to operate through a small gap between them, the light source thus travelling with the rollers 35 and 36 so that, as the rollers move over the surface and press the negative into very close contact with the paper at the local point between the rollers, the exposure is made.

The grip of the clip 2 is aided by a row of spikes 43 (see FIG. 4) projecting outwardly from the backing 8, the purpose of the spikes 43 being to firmly hold the photo-conductor paper or sheet 7 along its top edge and to continue to so hold it during the time the clip 2 is released to place the negative in position, reinstatement of the clip then also forcing the top edge of the negative on to the spikes to hold same firmly. The clip 2 has apertures 44 at the spike localities.

A high voltage generator for producing the corona or similar discharge may take any known form, the housing for such a generator being indicated by numeral 45 in the drawings. A lead 46 transfers the voltage to the shaft 19 of the roller 18.

Instead of using two passes of the carrier, charging and exposure can be effected on the one traverse, the negative in that case being in place on the xerographic paper or sheet and charging taking place through this with exposure to light immediately thereafter, or even simultaneously for it will be realised that if the negative has light intercepting sections through which charging can take place, the light will bleed away to charge in the remaining sections and will leave charged the sections where the light is intercepted. Such an arrangement may be particularly useful where prints are made from traced plans or the like, and is illustrated particularly in FIG. 5.

In this embodiment the light source 50 has the charging points 51 mounted on a member 52 adjacent the light source so that the corona effect passes to the xerographic sheet 53 between the two rubber rollers 54- and 55 which are pressed against the negative 56 to hold it down firmly on to the sheet 53 on the conductive plate 57. Springs 58 held on blocks 59 secured to the ends of the carrier 66 urge the rollers 54 and 55 against the negative 56.

The light source St) is again disposed in a housing 63 having a slot s4, a split sleeve 65 encircling the housing 63 to control the amount of light reaching the charging and exposing area 65. The member 52 is mount ed on insulation blocks 66 and the necessary charging voltage will be applied between the member 52 and the plate 57.

It will be realised that the light source may be in, or close to, the ultra-violet end of the spectrum which shows the most satisfactory response to the charge on the paper. The light source will of course be arranged to shine on the long area across the entire frame and the density can then readily be controlled by variation of either the eflective size of the slot through which the light issues or the speed of movement of the light source.

While in the foregoing descriptions the light source 30 or 59 is shown independently of the charging roller 18 or the charging points 51, the light source itself can charge the paper by having the light source of such a nature that it can provide a corona discharge to charge the paper when the appropriate voltage is applied to the light source, it being known that the use of an evacuated tube or a gas-filled tube can have the function of producing light when a particular voltage is applied thereto, but variation of this can produce a corona discharge.

What we claim is:

1. An improved charging and printing unit for electrophotographic processes comprising a main frame, a back ing plate of electrically conductive material carried by the said frame, means on said frame to hold a photoconductor sheet and negative on said backing plate, a

pair of tracks on said frame extending along two opposite sides of said backing plate, a carrier movable on said tracks, means to move said carrier across said backing plate from end to end, charging means on said carrier extending across said plate but insulated from said carrier, means to apply electrical potential between said charging means and the said plate, a housing and light 4- source on said carrier also spaced from said plate and extending across said plate, a slot in said housing facing said plate, and a pair of resilient pressure rollers mounted on said carrier to contact said plate on each side of said light source and press said negative and photo conductor sheet on to said plate.

2. An improved charging and printing unit for electrophotographic processes comprising a main frame, a backing plate of electrically conductive material carried by said frame, means on said frame to hold a photoconductor sheet and negative on said backing plate, a pair of tracks on said frame extending along two opposite sides of said backing plate, a carrier movable on said track, a pair of chains adjacent said tracks coupled to said carrier, sprockets on said frame to support said chains, means to drive said chains to move said carrier across said backing plate from end to end, a charging roller rotatably mounted on said carrier to extend across said plate but insulated from said carrier, driving means to revolve the roller when said carrier is moved over said plate, means to apply electrical potential between said charging roller and said plate, a housing and light source on said carrier also spaced from said plate and extending across said plate, a slot in said housing facing said plate, means to vary the effective width of the slot in the housing, and means to press said negative and photo-conductor sheet on to said plate.

3. An improved charging and printing unit for electrophotographic processes comprising a main frame, a backing plate of electrically conductive material carried by said frame, means on said frame to hold a pl1oto-conduc tor sheet and negative on said backing plate, a carrier movable on said frame, means to move said carrier across said backing plate from end to end, a charging roller rotatably mounted on said carrier to extend across said plate but insulated from said carrier, a resilient insulating driving member engaging said charging roller and said plate to revolve said charging roller when said carrier is moved over said plate, means to apply electrical potential between said charging roller and said plate, a housing and a light source on said carrier also spaced from said plate and extending across said plate, a light slot in said housing facing said plate, a slotted sleeve on said housing adjustable to vary the effective width of the slot in the housing, and a pair of resilient pressure rollers mounted on said carrier to contact said plate on each side of said light source and press said negative and photo-conductor sheet on to said plate.

4. An improved charging and printing unit for electrophotographic processes comprising a main frame, a backing plate of electrically conductive material carried by said frame, means on said frame to hold a photo-conductor sheet and negative on said backing plate, a pair of tracks on said frame extending along two opposite sides of said backing plate, a carrier movable on said track, a pair of chains adjacent said tracks coupled to said carrier, sprockets on said frame to support said chains, means to drive said chains to move said carrier across said backing plate from end to end, a charging roller rotatably mounted on said carrier to extend across said plate but insulated from said carrier, a resilient insulating driving member engaging said charging roller and said plate to revolve said charging roller when said carrier is moved over said plate, means to apply electrical potential between said charging roller and said plate, a housing and a light source on the said carrier also spaced from said plate and extending across said plate, a slot in said housing facing said plate, a slotted sleeve on said housing adjustable to vary the effective width of the slot in the housing, and a pair of resilient pressure rollers mounted on said carrier to contact said plate on each side of said light source and press said negative and photo-conductor sheet on to said plate.

5. An improved charging and printing unit for electrophotographic processes comprising a main frame, a backing plate of electrically conductive material carried by said frame, means on said frame to hold a photo-conductor sheet and negative on said backing plate, a pair of tracks on said frame extending along two opposite sides of said backing plate, a carrier movable on said track, means to move said carrier across said backing plate from end to end, a housing and light source on said carrier spaced from said plate and extending across said plate, a slot in said housing facing said plate, a charging member within the housing in the path of the light directed to said plate, means to apply electrical potential between said charging member and said plate, and a pair of resilient pressure rollers mounted on said carrier to contact said plate on each side of said light source and charging means to press said negative and photo-conductor sheet on to said plate.

References Cited in the file of this patent UNETED STATES PATENTS 

1. AN IMPROVED CHARGING AND PRINTING UNIT FOR ELECTROPHOTOGRAPHIC PROCESSES COMPRISING A MAIN FRAME, A BACKING PLATE OF ELECTRICALLY CONDUCTIVE MATERIAL CARRIED BY THE SAID FRAME, MEANS ON SAID FRAME TO HOLD A PHOTOCONDUCTOR SHEET AND NEGATIVE ON SAID BACKING PLATE, A PAIR OF TRACKS ON SAID FRAME EXTENDING ALONG TWO OPPOSITE SIDES OF SAID BACKING PLATE, A CARRIER MOVABLE ON SAID TRACKS, MEANS TO MOVE SAID CARRIER ACROSS SAID BACKING PLATE FROM END TO END, CHARGING MEANS ON SAID CARRIER EXTENDING ACROSS SAID PLATE BUT INSULATED FROM SAID CARRIER, MEANS TO APPLY ELECTRICAL POTENTIAL BETWEEN SAID CHARGING MEANS AND THE SAID PLATE, A HOUSING AND LIGHT SOURCE ON SAID CARRIER ALSO SPACED FROM SAID PLATE AND EXTENDING ACROSS SAID PLATE, A SLOT IN SAID HOUSING FACING SAID PLATE, AND A PAIR OF RESILIENT PRESSURE ROLLERS MOUNTED ON SAID CARRIER TO CONTACT SAID PLATE ON EACH SIDE OF SAID LIGHT SOURCE AND PRESS SAID NEGATIVE AND PHOTOCONDUCTOR SHEET ON TO SAID PLATE. 